Optical spin orientation of minority holes in a modulation-doped GaAs/(Ga,Al)As quantum well

Abstract

The optical spin orientation effect in a GaAs/(Ga,Al)As quantum well containing a high-mobility 2D electron gas was found to be due to spin-polarized minority carriers, the holes. The observed oscillations of both the intensity and polarization of the photoluminescence in a magnetic field are well described in a model whose main elements are resonant absorption of the exciting light by the Landau levels and mixing of the heavy-and light-hole subbands. After subtraction of these effects, the observed influence of magnetic fields on the spin polarization can be well interpreted by a standard approach of the optical orientation method. The spin relaxation of holes is controlled by the Dyakonov-Perel' mechanism. Deceleration of the spin relaxation by the magnetic field occurs through the Ivchenko mechanism -due to the cyclotron motion of holes. Mobility of holes was found to be two orders of magnitude smaller than that of electrons, being determined by the scattering of holes upon the electron gas.

Nuclear data - an essential tool in nuclear astrophysics

“…Then the situation is decisively di↵erent as thermal excitations mix orbitals across the shell gap and unblock the GT transitions. This was confirmed in two independent calculations for neutron-rich N = 50 nuclei using a thermal Quasiparticle Random Phase Approximation (QRPA) approach [88,89], in agreement with the earlier results obtained within the SMMC studies [58,84].…”

“…At N = 50 the situation is di↵erent, as cross-shell correlations are too weak to unblock the GT strength, as experimentally demonstrated for 86 Kr and 88 Se, which show vanishing GT strength for the ground state [86,87]. However, in the collapsing core N = 50 nuclei are only abundant at relatively high temperatures (T ⇠ 1 MeV).…”

Anomalous magnetic suppression of spin relaxation in a two-dimensional electron gas in a GaAs/AlGaAs quantum well

“…Interestingly, it was reported in Ref. [31] that for quasiresonant excitation of the 2DEG the electrons recombine with mobile holes which results in the separation between the PL lines of 2.1 meV/T equal to the sum of the electron and hole cyclotron energies.…”

Raman spectrum study of δ -doped GaAs/AlAs multiple-quantum wells

“…[25,26] The development of multiband envelope-function-approximation theory has successfully settled the controversy and been applied well to semiconductor multiple quantum well structures, through which the theoretical results for valence subbands are in good agreement with the experimental measurements. [27,28] In order to find the parameters E p , |V |, and E e from the evaluation of our Raman spectra measured, the information stored in the lineshape of each individual spectrum is used: the upper I + and lower I − branch coupling modes are simulated using Eq. ( 2); the luminescence background and the sharp bare LO-phonon line are fitted by sums of Gauss and Lorentz functions.…”